Ethyl acetate and water extracts of several tropical and sub-tropical blue-green algae, viz. Tolypothrix conglutinata, Schizothrix calcicola, and Crinalium sp. from Fanning Island, a Lyngbya sp. from Hawaii, and a Phormidium sp. from Molokai, exhibit good activity (% T/C greater than 170) against P-388 lymphocytic leukemia in mice. Using the P-388 bioassay in our laboratory to monitor the fractionations, anticancer compounds will be isolated from the cultured cyanophytes since adequate amounts are not available in the field. Molecular structures will be elucidated by a combination of chemical and physical methods. Pure anticancer compounds will be sent to NCI laboratories for chemotherapeutic evaluations.